Flexible phase change film and preparation method and application thereof

Abstract

The invention discloses a flexible phase change film and a preparation method and application thereof, and belongs to the technical field of heat storage temperature control energy-saving new materials.A polymer framework of ethyl cellulose is combined with functional particles for light absorption and light reflection to load a phase change material, the phase change film is endowed with flexibility, meanwhile, light absorption and light reflection are achieved, and the flexible phase change film is prepared. And the overall heat storage capacity is further endowed by utilizing the energy storage and temperature control capacity of the phase change material, so that the high-efficiency all-season heat management phase change material which has flexibility, heat storage, light absorption and light reflection capacities and realizes refrigeration in high-temperature seasons and heat absorption and heat preservation in cold seasons is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy-saving materials for heat storage and temperature control, and particularly relates to a flexible phase change film and a preparation method and application thereof. BACKGROUND

[0002] The reason for the demand of building thermal management is largely due to the lack of effective control of the thermal effect of sunlight. For example, in hot summer, reducing light input is conducive to building refrigeration; while in cold winter, increasing light input is conducive to building insulation. Therefore, constructing an integrated all-season thermal management material that can cool in high temperature season and keep warm in cold season, and can balance efficient light absorption and light reflection, has important promoting effect on reducing the energy consumption of buildings, alleviating the global energy situation and achieving the double carbon goal.

[0003] In the existing technology, the sunlight can be effectively reflected by radiation refrigeration, thereby reducing the surface temperature of the object; in addition, the light absorption can be effectively improved by the design of carbon-based materials, thereby increasing the surface temperature of the object. However, the current technology has the following problems: the refrigeration / heating material itself lacks heat storage capacity, such as graphene heating film, which has extremely low heat capacity of heating element and extremely fast temperature rise, but once the power is off, the temperature drops extremely fast and cannot maintain the temperature, that is, it does not have heat storage capacity, so its cooling / heating performance seriously decreases or even disappears with the change of use temperature. In addition, the existing refrigeration materials or heating materials are difficult to balance efficient light reflection and light absorption, such as high-density polyethylene film, polymethylpentene film and polytetrafluoroethylene film, which have extremely high solar reflectivity, but they cannot convert light energy into heat energy, that is, they cannot realize light absorption. SUMMARY

[0004] The present application provides a flexible phase change film and a preparation method and application thereof, which effectively solves the technical problems that the existing refrigeration / heating materials do not have heat storage capacity and are difficult to balance efficient light absorption and light reflection, and provides an integrated all-season thermal management flexible phase change film that balances efficient light absorption and light reflection.

[0005] The first object of the present application is to provide a flexible phase change film, taking a reflection-absorption film as a carrier, and loading a phase change material on the reflection-absorption film to form a flexible phase change film.

[0006] The preparation method of the reflection-absorption film is as follows: taking ethyl cellulose as a skeleton, taking inorganic particles as a reflector, and obtaining a reflection carrier film through solvent evaporation phase inversion and self-settlement, taking carbon material as an absorber, and loading the carbon material on the reflection carrier film to obtain a reflection-absorption film.

[0007] The inorganic particles are one or more of silicon oxide, aluminum oxide, titanium oxide and barium sulfate; and the carbon material is carboxylated single-walled carbon nanotube or carboxylated multi-walled carbon nanotube.

[0008] The phase change material is one or more of paraffin, alkanes, polyethylene glycol, fatty alcohols, and fatty acids.

[0009] In a preferred embodiment, the mass ratio of the phase change material to the reflective-absorbent film is 5 to 10:1.

[0010] In a preferred embodiment, the mass ratio of ethyl cellulose to inorganic particles is 1 to 9:1.

[0011] In a preferred embodiment, the mass ratio of ethyl cellulose to inorganic particles is 3:1.

[0012] A second objective of this invention is to provide a method for preparing the flexible phase change film described in any of the above claims, comprising the following steps: Using ethyl cellulose as the backbone and inorganic particles as the reflector, a reflective carrier film is obtained through solvent evaporation phase transformation and self-settling. Carbon material is used as the absorber, and carbon material is loaded onto the reflective carrier film to obtain a reflective-absorbent film. A flexible phase change film is obtained by loading a phase change material onto the reflective-absorbent film through vacuum impregnation.

[0013] In a preferred embodiment, the preparation method of the reflective-absorption film is as follows: an ethanol aqueous solution of ethyl cellulose is mixed with the inorganic particles, and the mixture is allowed to stand for 24 h to 48 h to obtain a reflective carrier film. An ethanol solution of carbon material with a concentration of 0.5% to 3% is sprayed onto the reflective carrier film at a spraying pressure of 0.5 MPa to 2 MPa, and then dried at room temperature to obtain the reflective-absorption film.

[0014] As a preferred embodiment, with 1cm 2 The amount of ethanol solution of the carbon material sprayed onto the reflective carrier film is 1 mL to 3 mL.

[0015] In a preferred embodiment, the amount of ethanol solution of the carbon material sprayed is 2 mL.

[0016] As a preferred embodiment, the preparation method of the flexible phase change film is as follows: at 80℃~100℃ and a vacuum degree of -0.1MPa, the phase change material is melted into a liquid state and vacuum impregnated onto the reflective-absorption film to obtain the flexible phase change film.

[0017] The third objective of this invention is to provide an application of the above-mentioned flexible phase change membrane in the preparation of refrigeration and heat insulation materials or heating and heat storage materials for use in refrigeration and heat storage equipment.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing a flexible phase change membrane. Using ethyl cellulose as a framework and inorganic particles as reflectors, a reflective carrier membrane is obtained through solvent evaporation, phase inversion, and self-settling. Carbon material is then loaded onto the reflective carrier membrane as an absorber to obtain a reflective-absorption membrane. Finally, a phase change material is loaded onto the reflective-absorption membrane through vacuum impregnation to obtain a flexible phase change membrane. This invention utilizes the polymer framework of ethyl cellulose combined with inorganic particles that absorb and reflect light to load the phase change material, giving the phase change membrane flexibility while achieving both light absorption and reflection. The energy storage and temperature control capabilities of the phase change material further endow it with overall heat storage capacity. This results in a highly efficient, all-season thermal management phase change material that combines flexibility, heat storage, light absorption, and light reflection capabilities, enabling cooling in high-temperature seasons and heat absorption and insulation in cold seasons.

[0019] The phase change membrane obtained by this invention possesses excellent flexibility and can be integrated into various complex interfaces, effectively improving its operability. The phase change membrane obtained by this invention balances efficient light absorption and light reflection, enabling surface cooling of the target system in high-temperature weather and effective heating of the target system in cold weather. The phase change membrane obtained by this invention exhibits superior energy storage density, further enabling thermal storage and temperature control, reducing the thermal comfort energy consumption of the target system.

[0020] The flexible phase change membrane prepared by this invention has good flexibility and can be bent more than 180° while maintaining its shape without breaking; it has significantly improved solar reflectivity and absorbance, with the reflective layer having a reflectivity of more than 80% in the visible light band and the absorbance of the absorption layer having an absorbance of more than 1 in the ultraviolet-visible light band; the flexible phase change membrane of this invention has excellent heat storage capacity, with a phase change enthalpy of more than 110 J / g. Attached Figure Description

[0021] Figure 1 The diagram shows the structure and working principle of the flexible phase change film prepared according to the present invention.

[0022] Figure 2 Differential scanning calorimetry curve of the flexible phase change film prepared in this invention.

[0023] Figure 3 This is the reflectance spectrum of the flexible phase change film prepared according to the present invention.

[0024] Figure 4 The absorbance spectrum of the flexible phase change film prepared in this invention is shown. Detailed Implementation

[0025] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0026] As mentioned in the background section of this invention, existing cooling / heating materials lack heat storage capacity, resulting in a significant decrease or even loss of cooling / heating performance with changes in operating temperature. Furthermore, existing technologies lack integrated materials that simultaneously achieve efficient light absorption and reflection; most existing material systems are coatings / blocks, rigid or directly bonded to objects, lacking further disassembly and operability. To address these technical problems, this invention provides a flexible phase change film, its preparation method, and its applications.

[0027] The technical solution of the present invention will be analyzed and described in detail below.

[0028] This invention first provides a flexible phase change film, which uses a reflective-absorption film as a carrier and loads a phase change material onto the reflective-absorption film to form a flexible phase change film. Its structure and working principle are as follows: Figure 1 As shown.

[0029] The method for preparing the reflective-absorption membrane is as follows: using ethyl cellulose as the skeleton and inorganic particles as the reflector, a reflective carrier membrane is obtained through solvent evaporation, phase transformation, and self-settling; carbon material is used as the absorber, and the carbon material is loaded onto the reflective carrier membrane to obtain the reflective-absorption membrane.

[0030] The inorganic particles are one or more of silicon oxide, aluminum oxide, titanium oxide, and barium sulfate; the carbon material is a carboxylated single-walled carbon nanotube or a carboxylated multi-walled carbon nanotube.

[0031] The phase change material is one or more of paraffin, alkanes, polyethylene glycol, fatty alcohols, and fatty acids.

[0032] For the aforementioned phase change material, the polyethylene glycol has a molecular weight of 1000-20000, the fatty alcohol is a fatty alcohol with 14-18 carbon atoms, and the fatty acid is a fatty acid with 14-18 carbon atoms.

[0033] The average particle size of the inorganic particles is 100nm to 1000nm, more preferably 200nm to 500nm, and the dispersion and self-settling effect is best when the average particle size is 300nm to 400nm.

[0034] In the above technical solution, a phase change material (PCM) is loaded onto a polymer backbone of ethyl cellulose, incorporating functional particles that absorb and reflect light. This endows the PCM with flexibility while simultaneously achieving light absorption and reflection. Furthermore, the energy storage and temperature control capabilities of the PCM further enhance its overall heat storage capacity. This results in a highly efficient, all-season thermal management PCM that combines flexibility, heat storage, light absorption, and light reflection, enabling both cooling in high-temperature seasons and heat absorption and insulation in cold seasons. The PCM obtained by this invention balances efficient light absorption and reflection, allowing for surface cooling of the target system in high-temperature weather and effective heating of the target system in cold weather.

[0035] To prepare a flexible phase change membrane with good radiative cooling efficiency, the mass ratio of ethyl cellulose to inorganic particles is 1–9:1. The optimal radiative cooling efficiency is achieved when the ratio is 3:1. When the mass ratio of ethyl cellulose exceeds the specified 9, the inorganic particles cannot fully cover the reflective layer, resulting in a linear decrease in reflectivity and a significant reduction in radiative cooling capacity (as in Comparative Example 1). When the mass ratio of ethyl cellulose is less than the specified 1, the inorganic particles occupy a large amount of space in the ethyl cellulose, affecting the phase change material load, significantly reducing the phase change enthalpy, and lacking flexibility (as in Comparative Example 2).

[0036] This invention also provides a method for preparing a flexible phase change film, comprising the following steps: Using ethyl cellulose as the backbone and inorganic particles as the reflector, a reflective carrier film is obtained through solvent evaporation, phase transformation, and self-settling. Carbon material is used as the absorber, and the carbon material is loaded onto the reflective carrier film to obtain a reflective-absorbent film.

[0037] A flexible phase change film is obtained by loading a phase change material onto the reflective-absorbent film through vacuum impregnation.

[0038] It should be noted that the specific preparation method of the reflective-absorption film is as follows: The inorganic particles are mixed in an ethanol-water solution of ethyl cellulose and allowed to stand for 24-48 hours to obtain a reflective carrier film. A carbon material ethanol solution with a concentration of 0.5%-3% is sprayed onto the reflective carrier film at a spraying pressure of 0.5-2 MPa, and then dried at room temperature to obtain the reflective-absorption film. When preparing the above reflective carrier film, a standing time of 30-36 hours yields a reflective film carrier with a complete pore structure. During spraying, a more preferred spraying pressure is 1-1.5 MPa, with the best spraying effect observed at 1 MPa. For the concentration of the carbon material ethanol solution, a more preferred concentration is 1%-2%, with the best spraying effect observed at 1%.

[0039] To obtain a flexible phase change film with good light absorption capacity, a 1cm... 2The reflective carrier film is prepared by spraying an ethanol solution of carbon material at a rate of 1 mL to 3 mL. The flexible phase change film exhibits optimal light absorption when the spraying amount is 2 mL. When the spraying amount of the ethanol solution of carbon material is less than the specified 1 mL, insufficient coverage of the absorption layer results in reduced absorbance (consistent with the concentration reduction in Comparative Example 4). When the spraying amount of the ethanol solution of carbon material exceeds the specified 3 mL, it occupies the loading space of the phase change material, leading to a decrease in the phase change enthalpy, reduced flexibility, and instability of the carbon nanotubes on the surface, with some directly detaching (consistent with the concentration reduction in Comparative Example 5).

[0040] It should be noted that the specific preparation method of the flexible phase change film is as follows: at 80℃~100℃ and a vacuum degree of -0.1MPa, the phase change material is melted into a liquid state and vacuum impregnated into the reflective-absorption film to obtain the flexible phase change film. During the above vacuum impregnation process, the mass ratio of the phase change material to the reflective-absorption film is 5~10:1. When the mass ratio of the phase change material is less than 5 (as defined here), the melted phase change material cannot completely cover the carrier, resulting in a decrease in the mass fraction of the phase change material and a decrease in the phase change enthalpy in the final flexible phase change film. When the mass ratio of the phase change material is greater than 10 (as defined here), there is too much phase change material, and some of it will accumulate on the material surface, causing leakage and reducing flexibility.

[0041] The technical effects of the present invention will be described below through specific embodiments and comparative examples.

[0042] Example 1 A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve. Then add 0.2g of barium sulfate particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.05g of carboxylated single-walled carbon nanotubes and disperse them in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0043] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin turns into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a flexible phase change film.

[0044] Depend on Figures 2-4It can be seen that the flexible phase change film prepared in Example 1 of the present invention has a melting enthalpy of approximately 130 J / g, and its differential scanning calorimetry curve is as follows. Figure 2 It has good flexibility and can be bent approximately 180° without breaking; the reflective layer has a solar reflectivity exceeding 90%. Figure 3 (Reflectance spectrum), the absorbance of the absorption layer exceeds 1.7 ( Figure 4 (Absorbance spectrum).

[0045] Example 2 A method for preparing a flexible phase change film includes the following steps: S1, 1g of ethyl cellulose was weighed and added to a mixed solution of 1g water and 8g ethanol, stirred for 2 hours to dissolve, then 0.5g of alumina particles (average diameter 300nm) was added and stirred for 2 hours to obtain a uniform suspension. This suspension was allowed to stand in a petri dish for 30 hours to obtain a reflective film carrier. 0.1g of carboxylated single-walled carbon nanotubes were dispersed in 4.9g ethanol to obtain a spraying solution. This solution was sprayed onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0046] S2, 0.5g of the reflective-absorption membrane and 10g of polyethylene glycol (molecular weight 4000) are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the polyethylene glycol is transformed into a liquid state and impregnated with the reflective-absorption membrane for 3h. Finally, the excess polyethylene glycol on the surface is removed to obtain a flexible phase change membrane.

[0047] The flexible phase change film prepared in Example 2 of this invention has a melting enthalpy of approximately 110 J / g and exhibits good flexibility, capable of being bent approximately 180° without breaking. The reflective layer has a solar reflectivity exceeding 92%, and the absorbance of the absorption layer exceeds 2.

[0048] Example 3 A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.5g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 8.5g of ethanol. Stir for 2 hours to dissolve. Then add 0.1g of silica particles (average diameter 500nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 30 hours to obtain a reflective film carrier. Take 0.05g of carboxylated single-walled carbon nanotubes and disperse them in 9.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0049] S2, 0.5g of the reflective-absorption membrane and 3g of eicosane are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C temperature, the eicosane is transformed into a liquid state and impregnates the reflective-absorption membrane for 3 hours. Finally, the excess eicosane on the surface is removed to obtain a flexible phase change membrane.

[0050] The flexible phase change film prepared in Example 3 of this invention has a melting enthalpy of approximately 140 J / g and exhibits good flexibility, capable of being bent approximately 180° without breaking. The reflective layer has a solar reflectivity exceeding 85%, and the absorbance of the absorption layer exceeds 1.2.

[0051] Example 4 A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.9g of ethyl cellulose and add it to a mixed solution of 1.1g of water and 8g of ethanol. Stir for 2 hours to dissolve, then add 0.3g of barium sulfate particles (average diameter 300nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.1g of carboxylated multi-walled carbon nanotubes and disperse them in 4.9g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0052] S2, 0.5g of the reflective-absorption membrane and 4g of tetradecyl alcohol are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C temperature, the tetradecyl alcohol is converted into a liquid state and impregnates the reflective-absorption membrane for 3h. Finally, the excess eicosane on the surface of the reflective-absorption membrane is removed to obtain a flexible phase change membrane.

[0053] The flexible phase change film prepared in Example 4 of this invention has a melting enthalpy of about 120 J / g, good flexibility, and can be bent about 180° without breaking; the reflective layer has a solar reflectivity of more than 95%, and the absorbance of the absorption layer exceeds 2.2.

[0054] Example 5 A method for preparing a flexible phase change film includes the following steps: S1, weigh 1g of ethyl cellulose and add it to a mixed solution of 1g water and 8g ethanol. Stir for 2 hours to dissolve, then add 0.5g of titanium dioxide particles (average diameter 300nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.05g of carboxylated multi-walled carbon nanotubes and disperse them in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, applying it to every 1cm of surface area. 22 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0055] S2, 0.5g of the reflective-absorption membrane and 4g of tetradecanoic acid are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the tetradecanoic acid is used to impregnate the reflective-absorption membrane for 3 hours. Finally, the excess eicosane on the surface of the reflective-absorption membrane is removed to obtain a flexible phase change membrane.

[0056] The flexible phase change film prepared in Example 5 of this invention has a melting enthalpy of about 130 J / g, good flexibility, and can be bent about 180° without breaking; the reflective layer has a solar reflectivity of over 90%, and the absorbance of the absorption layer exceeds 1.8.

[0057] To further demonstrate the technical effects of the present invention, a comparative example is also provided, as follows: Comparative Example 1 The difference from Example 1 is that the mass ratio of ethyl cellulose to barium sulfate particles is limited to 10:1.

[0058] A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve. Then add 0.08g of barium sulfate particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.05g of carboxylated single-walled carbon nanotubes and disperse them in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0059] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin turns into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a flexible phase change film.

[0060] The flexible phase change film prepared in Comparative Example 1 of this invention has a melting enthalpy of about 135 J / g, good flexibility, and can be bent about 180° without breaking; the solar reflectivity of the reflective layer is less than 40%, and the absorbance of the absorption layer exceeds 1.7.

[0061] Comparative Example 2 The difference from Example 1 is that the mass ratio of ethyl cellulose to barium sulfate particles is limited to 0.8:1.

[0062] A method for preparing a phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve, then add 1g of barium sulfate particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.05g of carboxylated single-walled carbon nanotubes and disperse them in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0063] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin is transformed into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a phase change film.

[0064] The phase change film prepared in Comparative Example 2 of this invention has a melting enthalpy of about 85 J / g, lacks flexibility, and breaks when bent; the reflective layer has a solar reflectivity of over 80%, and the absorbance of the absorption layer exceeds 1.7.

[0065] Comparative Example 3 The difference from Example 1 is that magnesium oxide was chosen as the inorganic particle.

[0066] A method for preparing a phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve, then add 0.2g of magnesium oxide particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.05g of carboxylated single-walled carbon nanotubes and disperse them in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0067] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin is transformed into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a phase change film.

[0068] The flexible phase change film prepared in Comparative Example 3 of this invention has a melting enthalpy of about 100 J / g, lacks flexibility, and breaks when bent; the reflective layer has a solar reflectivity of less than 50%, and the absorbance of the absorption layer exceeds 1.7.

[0069] Comparative Example 4 The difference compared to Example 1 is that the concentration of the ethanol solution of carboxylated single-walled carbon nanotubes was reduced to 0.4%.

[0070] A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve, then add 0.2g of magnesium oxide particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.04g of carboxylated single-walled carbon nanotubes and disperse them in 4.96g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0071] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin turns into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a flexible phase change film.

[0072] The flexible phase change film prepared in Comparative Example 4 of this invention has a melting enthalpy of about 130 J / g, good flexibility, and can be bent about 180° without breaking; the reflective layer has a solar reflectivity of over 90%, and the absorbance of the absorption layer is less than 0.8.

[0073] Comparative Example 5 The difference compared to Example 1 is that the concentration of the ethanol solution of carboxylated single-walled carbon nanotubes is increased to 4%.

[0074] A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve, then add 0.2g of magnesium oxide particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain a reflective film carrier. Take 0.2g of carboxylated single-walled carbon nanotubes and disperse them in 4.8g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, with a spraying depth of 1cm. 22 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0075] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin turns into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a flexible phase change film.

[0076] The flexible phase change film prepared in Comparative Example 5 of this invention has a melting enthalpy of about 100 J / g, and has a certain degree of flexibility. It can be bent at about 120° without breaking, but breaks at 180°. The carbon nanotubes cannot be stably present on the surface and some fall off directly. The reflective layer has a solar reflectivity of over 90%, and the absorbance of the absorption layer is about 2.1.

[0077] Comparative Example 6 The difference compared to Example 1 is that a 1% graphene oxide ethanol solution was selected as the spraying liquid.

[0078] A method for preparing a flexible phase change film includes the following steps: S1, weigh 0.8g of ethyl cellulose and add it to a mixed solution of 1.5g of water and 7.7g of ethanol. Stir for 2 hours to dissolve. Then add 0.2g of magnesium oxide particles (average diameter 400nm) and stir for 2 hours to obtain a uniform suspension. Let the suspension stand in a petri dish for 36 hours to obtain the reflective film carrier. Disperse 0.05g of graphene oxide in 4.95g of ethanol to obtain a spraying solution. Spray the spraying solution onto the surface of the reflective film carrier at a spraying pressure of 1MPa, applying it to every 1cm of surface area. 2 2 mL of spraying liquid was sprayed onto the reflective film carrier and dried at room temperature to obtain the reflective-absorption film.

[0079] S2, 0.5g of the reflective-absorption film and 2.5g of paraffin are placed together in a vacuum oven. Under the conditions of -0.1MPa vacuum and 80°C, the paraffin turns into a liquid state and impregnates the reflective-absorption film for 3 hours. Finally, the excess paraffin on the surface of the reflective-absorption film is removed to obtain a flexible phase change film.

[0080] The flexible phase change film prepared in Example 1 of this invention has a melting enthalpy of about 120 J / g, and has a certain degree of flexibility. It can be bent at about 150° without breaking, and breaks at 180°. The solar reflectivity of the reflective layer can exceed 90%, and the absorbance of the absorption layer is about 0.7.

[0081] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A flexible phase change film, characterized in that, A flexible phase change film is formed by loading a phase change material onto a reflective-absorption film as a carrier. The method for preparing the reflective-absorption membrane is as follows: using ethyl cellulose as the skeleton and inorganic particles as the reflector, a reflective carrier membrane is obtained through solvent evaporation, phase transformation, and self-settling; carbon material is used as the absorber, and the carbon material is loaded onto the reflective carrier membrane to obtain the reflective-absorption membrane. The inorganic particles are one or more of silicon oxide, aluminum oxide, titanium oxide, and barium sulfate; the carbon material is a carboxylated single-walled carbon nanotube or a carboxylated multi-walled carbon nanotube. The phase change material is one or more of paraffin, alkanes, polyethylene glycol, fatty alcohols, and fatty acids.

2. The flexible phase change film according to claim 1, characterized in that, The mass ratio of the phase change material to the reflective-absorption film is 5 to 10:

1.

3. The flexible phase change film according to claim 1, characterized in that, The mass ratio of ethyl cellulose to inorganic particles is 1 to 9:

1.

4. The flexible phase change film according to claim 3, characterized in that, The mass ratio of ethyl cellulose to inorganic particles is 3:

1.

5. A method for preparing a flexible phase change film according to any one of claims 1 to 4, characterized in that, Includes the following steps: Using ethyl cellulose as the backbone and inorganic particles as the reflector, a reflective carrier film is obtained through solvent evaporation phase transformation and self-settling. Carbon material is used as the absorber, and carbon material is loaded onto the reflective carrier film to obtain a reflective-absorbent film. A flexible phase change film is obtained by loading a phase change material onto the reflective-absorbent film through vacuum impregnation.

6. The method for preparing a flexible phase change film according to claim 5, characterized in that, The specific preparation method of the reflective-absorption membrane is as follows: an ethanol aqueous solution of ethyl cellulose is mixed with the inorganic particles, and the mixture is allowed to stand for 24h to 48h to obtain a reflective carrier membrane. An ethanol solution of carbon material with a concentration of 0.5% to 3% is sprayed onto the reflective carrier membrane at a spraying pressure of 0.5MPa to 2MPa, and then dried at room temperature to obtain the reflective-absorption membrane.

7. The method for preparing a flexible phase change film according to claim 6, characterized in that, With 1cm 2 The amount of ethanol solution of the carbon material sprayed onto the reflective carrier film is 1 mL to 3 mL.

8. The method for preparing a flexible phase change film according to claim 7, characterized in that, The amount of ethanol solution of the carbon material sprayed is 2 mL.

9. The method for preparing a flexible phase change film according to claim 5, characterized in that, The specific preparation method of the flexible phase change film is as follows: at 80℃~100℃ and a vacuum degree of -0.1MPa, the phase change material is melted into a liquid state and vacuum impregnated on the reflection-absorption film to obtain the flexible phase change film.

10. The application of the flexible phase change membrane according to claims 1 to 4 in the preparation of refrigeration and heat insulation materials or heating and heat storage materials for use in refrigeration and heat storage equipment.

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